The present invention relates, in general, to a prostate-specific antigen, PCA3. In particular, the present invention relates to nucleic acid molecules coding for the PCA3 protein; purified PCA3 proteins and polypeptides; recombinant nucleic acid molecules; cells containing the recombinant nucleic acid molecules; antibodies having binding affinity specifically to PCA3 proteins and polypeptides; hybridomas containing the antibodies; nucleic acid probes for the detection of nucleic acids encoding PCA3 proteins; a method of detecting nucleic acids encoding PCA3 proteins or polypeptides in a sample; kits containing nucleic acid probes or antibodies; bioassays using the nucleic acid sequence, protein or antibodies of this invention to diagnose, assess, or prognose a mammal afflicted with prostate cancer; therapeutic uses; and methods of preventing prostate cancer in an animal.